From 8339f0008c47cdd921c73f6d53d5588b5484f93c Mon Sep 17 00:00:00 2001 From: "Eric W. Biederman" Date: Mon, 29 Jan 2007 13:19:05 -0700 Subject: [PATCH] [PATCH] i386: In assign_irq_vector look at all vectors before giving up When the world was a simple and static place setting up irqs was easy. It sufficed to allocate a linux irq number and a find a free cpu vector we could receive that linux irq on. In those days it was a safe assumption that any allocated vector was actually in use so after one global pass through all of the vectors we would have none left. These days things are much more dynamic with interrupt controllers (in the form of MSI or MSI-X) appearing on plug in cards and linux irqs appearing and disappearing. As these irqs come and go vectors are allocated and freed, invalidating the ancient assumption that all allocated vectors stayed in use forever. So this patch modifies the vector allocator to walk through every possible vector before giving up, and to check to see if a vector is in use before assigning it. With these changes we stop leaking freed vectors and it becomes possible to allocate and free irq vectors all day long. This changed was modeled after the vector allocator on x86_64 where this limitation has already been removed. In essence we don't update the static variables that hold the position of the last vector we allocated until have successfully allocated another vector. This allows us to detect if we have completed one complete scan through all of the possible vectors. Acked-by: Auke Kok Signed-off-by: Eric W. Biederman Signed-off-by: Linus Torvalds --- arch/i386/kernel/io_apic.c | 32 +++++++++++++++++++------------- 1 file changed, 19 insertions(+), 13 deletions(-) diff --git a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c index 2424cc9c7b3d..6a3875f81a0a 100644 --- a/arch/i386/kernel/io_apic.c +++ b/arch/i386/kernel/io_apic.c @@ -1227,26 +1227,32 @@ static u8 irq_vector[NR_IRQ_VECTORS] __read_mostly = { FIRST_DEVICE_VECTOR , 0 } static int __assign_irq_vector(int irq) { - static int current_vector = FIRST_DEVICE_VECTOR, offset = 0; - int vector; + static int current_vector = FIRST_DEVICE_VECTOR, current_offset = 0; + int vector, offset, i; BUG_ON((unsigned)irq >= NR_IRQ_VECTORS); if (irq_vector[irq] > 0) return irq_vector[irq]; - current_vector += 8; - if (current_vector == SYSCALL_VECTOR) - current_vector += 8; - - if (current_vector >= FIRST_SYSTEM_VECTOR) { - offset++; - if (!(offset % 8)) - return -ENOSPC; - current_vector = FIRST_DEVICE_VECTOR + offset; - } - vector = current_vector; + offset = current_offset; +next: + vector += 8; + if (vector >= FIRST_SYSTEM_VECTOR) { + offset = (offset + 1) % 8; + vector = FIRST_DEVICE_VECTOR + offset; + } + if (vector == current_vector) + return -ENOSPC; + if (vector == SYSCALL_VECTOR) + goto next; + for (i = 0; i < NR_IRQ_VECTORS; i++) + if (irq_vector[i] == vector) + goto next; + + current_vector = vector; + current_offset = offset; irq_vector[irq] = vector; return vector; -- 2.34.1